Starting in the 1950's the paper converting art turned to log saws such as the oscillating disc saw of U.S. Pat. No. 2,752,999 colloquially known as the "Gilbertville" saw. Prior to that time, when manufacturing toilet paper and household toweling rolls, the webs were longitudinally slit during rewinding--as seen for example in U.S. Pat. No. 2,769,600. Rewinding consisted of unreeling a wide web (usually 63" wide or more--in multiples of the 41/2" width of toilet paper roll squares) from the parent or jumbo roll 5' or more in diameter. Prior to rewinding into retail-sized rolls, the web was transversely perforated and longitudinally slit on 41/2" centers (11" for towels). Because the web sometimes had defects such as "fish-eyes", viz., large holes in the web, wrinkles and caliper variations, it was possible for one or more of the 41/2" wide strips to suddenly become discontinuous. In a 63" wide rewinder (a polular size in the 1950's--corresponding to 14 -41/2" widths), this would mean then one slit web would suddenly stop advancing while the other 13 proceeded normally. Nonetheless, the rewinding operation had to be quickly stopped--with the web being advanced at 1,000 feet per minute, even the one discontinuous width could quickly jam the machine. This meant that the other webs would be stopped and the partially completed rolls jettisoned--resulting in considerable waste.
Another main problem on the machines with slitters was the difficulty in transferring 14 separate webs to the new core at continuous speeds of 1,000 feet per minute. Log sawing after the rewinder allowed the rewinder to transfer a single full width web, i.e., 63"--much easier and consistently.
Waste also occurred because the slitting could not be started until the web was fully threaded through the machine and on the ultimate cardboard cores. This meant that every start-up wasted both the unslit paper used to thread the machine and the cores on which this was wound. All of these problems were avoided by the Gilbertville log saw which operated on the "rewound" retail-sized log. For example, the nominal 63" wide web (the web was usually 66" wide to insure an inch or so trim along each edge) would be wound on an elongated cardboard core of the same length. The log was then removed from the rewinder to the log saw where it was indexed or stepped 41/2" at a time past the oscillating disc.
Because the disc was sawing through a log that approximated a wooden log 4-6" in diameter, it quickly became dull so that it was necessary to frequently renew the periphery. This was done by mounting abrasive wheels adjacent the periphery of the disc and selectively bringing the disc and wheels into contact--as seen in U.S. Pat. No. 2,766,566.
One of the drawbacks of the Gilbertville saw was the fact that its oscillating movement had to stop twice each cycle to reverse its movement. This limited production as well as requiring heavier parts to withstand the deceleration. The next improvement which overcame this difficulty was the orbital saw of U.S. Pat. No. 3,213,731.
In that patent, the disc followed an orbit wherein the logs were indexed along a path that was adjacent the nadir of the orbit. However, the disc movement still had to be stopped--now, however, to accommodate sharpening, but not during each cycle. The extent of the sharpening can be appreciated from the fact that the disc diameter when first installed was usually 21" but at the end of its working life was down to 18". The stopping of the orbital saw for sharpening was tolerable because this was coordinated with log indexing.
When production demands became greater, the indexing was discontinued and the disc moved through an orbit skewed relative to the log path--as shown in U.S. Pat. No. 4,041,813. To eliminate the need for any stoppage of the orbiting saw, the sharpening stones were moved with the saw, as with the Gilbertville saw. However, to move the sharpening stones with an orbital saw required a complicated mechanism to maintain the stones in a predetermined attitude relative to the saw (always above the saw)--a problem not present in the oscillating Gilbertville saw. According to the present invention, a novel linkage or interconnection is provided between the subframe supporting the stones and both the frame of the machine as well as the member which supports the saw eccentrically to provide the orbital motion. More particularly, this is achieved through the use of a pivotal and slidable connection between the machine frame and a pivotal connection between the saw mounting member. Further, in one preferred embodiment of the invention, the stones are freely journalled within the subframe and are equipped with adjustable limits so that uniform and controllable forces are applicable to opposite sides of the saw.
Other objects and advantages of the invention may be seen in the details of the ensuing specification.